Multi-objective optimization and performance analysis of a CPV/T system based on NSGA-II and entropy weight TOPSIS method

Abstract

This study presents a novel concentrating photovoltaic/thermal (CPV/T) system integrated with coaxial cross Kenics mixers to enhance performance. The solar concentration process was modeled using the Monte Carlo Ray Tracing method, while Computational Fluid Dynamics simulations and Response Surface Methodology were applied to analyze the effects of four key design variables: inlet velocity, gap between the receiver tube and the mixer, mixer pitch, and receiver tube diameter. Electrical efficiency, thermal efficiency, and performance evaluation criterion were defined as response indicators, and predictive models for each were developed. A thermodynamic optimization framework combining the NSGA-II algorithm with the entropy weighted TOPSIS method was used to identify the optimal system configuration. Optical simulation results show a uniform energy flux distribution on the solar cell surface. The system's optical efficiency decreases from 99.98 % to 47.31 % as the solar tracking error angle increases from 0.0° to 2.0°. The Response Surface Methodology based predictive models demonstrated high accuracy in capturing system behavior. Among the design variables, the receiver tube diameter had the most significant impact on electrical and thermal efficiencies, while the mixer pitch most strongly affected the performance evaluation criterion. Under an inlet velocity of 0.136 m s⁻¹, a gap between the receiver tube and the mixer of 0.75 mm, a mixer pitch of 15.01 mm, and a receiver tube diameter of 12.00 mm, the system achieves its highest overall performance. Compared to a system without the optimized mixers, electrical efficiency improved from 13.37 % to 14.55 %, and thermal efficiency increased from 58.03 % to 61.14 %.